This 'stumble' on initial accel. is the accelerator pump jet not the main
and secondary fuel and air jets. The amount and duration of the
'pump squirt' is controlled by the size of the jet.
This 'richening' function is the equivalent of the heavier spring
of the SU carb.
On initial accel. you need a bit of extra gas getting in to compensate
for the sudden pressure drop opening the buterfly
the stiff spring of the dashpot piston, fighting the vacuum, causes
vacuum to suck gas rather than air until the piston could move up
to allow air in, thus temporarily enriching the mixture.
On a DCOE, this is the same as the pump/accel and backbleed jets.
Paul Tegler wizardz@toad.net http://www.teglerizer.com
----- Original Message -----
From <Daniel1312 at aol.com>
To: <MartyWit@aol.com>; <spridgets@autox.team.net>
Sent: Tuesday, October 31, 2000 9:17 AM
Subject: Re: Weber DGV jet selection
Marty,
Who do you know the problem lies with the carb? When you say the flat spot
is just above idle what rpm is the carb idling at? Are you running an
ignition advance with the carb? Is the rest of the engine stock?
The problem is not going to be with the main jets because it is going to be
1800rpm upwards before they are working. Likewise I think you can forget the
secondary barrel. This only leaves a single idle jet to play around with and
you don't say what alternatives you have tried.
1312
In a message dated 31/10/00 02:20:51 GMT Standard Time, MartyWit@aol.com
writes:
<< What would be the recommended jets for a Weber DGV 5A to be used in a
stock
1275 engine? As delivered, the primary barrel had a 55 idle jet, 140 main
jet, and a 165 air corrector. The secondary barrel used a 50 idle jet, 135
main jet, and a 160 air corrector. My problem is a flat spot just above
idle, which usually causes the car to stall unless I blip the throttle
first.
Once on the move; however, the car runs fantastic, delivering both good
performance and economy. I've experimented with other sizes of all of the
above, but without fully eliminating the problem. Rather then spend more
money on more calibrated parts, I'd really like to know what jets work best
for anybody else out there also using a DGV. Thanks.
Marty
1970 MG Midget
1977 MG Midget
----------------------- Headers --------------------------------
Return-Path: <spridgets-owner@autox.team.net>
Received: from rly-xa05.mx.aol.com (rly-xa05.mail.aol.com [17 >>
|